This is the first I ever heard of paying to attend an air show. Though when I go it's at a USAF base. Not only free to get in, with free parking, but the USAF has airmen running buses and transport for the elderly and disabled for free as well. (Frankly, any service's event I have attended at a military base has been done well, not just the USAF)
If the money is to go to a non-profit, why not just give the NP's a free booth? I always chip in to the NP's, and try to pick up an item or two from the squads raising money for their funds, too. In my book, the best show souveniers are the squad items I buy from them.
Then I also -know_ where the money is going.
I also work for a non-profit that helps the disabled stay independent, and the NP booths are a great way to meet and network with other NP's in the area.